Update devel/php-composer to 1.6.3 and add php flavors

[madpilot]

Summary

I'd like the php-composer port to get flavors support, so it can
be used with any PHP version from binary packages.

While testing this I noticed a new version is available.

I've added an UPDATING entry, due to the package name change. I'd
like feedback if a better option is available to avoid the inconvenience
to users.

Related bug on bugzilla:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227418

Test Plan

Already tested in poudriere and my machines. Update path for the
binary package is manual at present.

[mat]

UPDATING

17 ↗

(On Diff #41323)

It would probably be better to tell people how to rename it:

pkg set -n php-composer:php56-composer

devel/php-composer/Makefile

8 ↗

(On Diff #41323)

I am not sure wether it should be PREFIX or SUFFIX.

SUFFIX should be used when it is an app, and PREFIX should be used for all other cases.

[madpilot]

Modified UPDATING message.

[madpilot]

devel/php-composer/Makefile

8 ↗

(On Diff #41323)

Well composer is a php package manager, allowing to have a description of the dependencies of a project and automatically download them and prepare autoload files.

So it is a developer tool, actually written in php language, but more a part of the language itself.

I used PREFIX simply because the port was already doing that and it looks correct to me.